I envy modern Christians for their ability to make up their faith by pretending the scriptures don’t exist. “I was taught that Jesus is love, therefore, if it makes me happy or gives me pleasure it can’t be a sin”
That is a straw man. I am sure you can find some one who says that somewhere out of billions of Christians, but it is effectively something no one says.
Nothing in there about "only if they meet certain moral standards".
I do agree that celebrating people because they do things that contradict Christ teachings (most commonly for accumulating wealth) is wrong.
> "Love your neighbour as yourself"
That is a very important part of that understanding of the meaning of love. While it also means that you love your neighbour in any circumstance, it importantly says that you should love the neighbour in the same way you love yourself. You love yourself even when you know you are evil and should die.
The stance of the (catholic) church is that you should damn the sin and love the sinner.
1 Timothy 6:20–21 – “O Timothy, keep that which is committed to thy trust, avoiding the profane novelties of words and oppositions of knowledge falsely so called, which some professing have erred concerning the faith.”
2 Timothy 4:3–4 – Warns of people turning from truth to myths, implying leaders must protect them from such influences.
Titus 1:9–11 – Bishops must “stop the mouths” of those teaching error, which includes preventing their works from spreading.
Acts 20:28–31 – Paul warns the Ephesian elders to guard the flock from false teachers who will arise “speaking perverse things.”
2 John 1:10–11 – “If any man come to you, and bring not this doctrine, receive him not into the house nor say to him, God speed you.”
Romans 16:17 – Mark and avoid those who cause doctrinal divisions; a list of banned works is a formal way of “marking” them.
Acts 19:19 – New converts in Ephesus publicly burn their occult books after coming to the faith.
Deuteronomy 13:1–5 – False prophets and their influence must be eradicated from the midst of the people.
Etc, etc, etc.
For that and other reasons there are plenty of things presented in the old testament as sins, which Christians don't consider to be sins. The most obvious example is probably rules around kosher food.